a tale of five computers

8/19/2019 A Tale of Five Computers

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P H O T O G R A P H

B Y

C A R O L Y N

D J A N O G L Y

Historical ReflectionsTom Kilburn: A Taleof Five Computers Reflections on a British computer engineer who influenced severalimportant machines, including the first stored-program computer.

Pythagoreans.a Speakers to the student

society included future Bletchley Parkcode breakers M.H.A. Newman,2,b K.J.

Le Couteur, and William T. Tutte. How-

ever, Kilburn would not have been like-

a Geoff Tootill was Christ’s College representa-

tive for the New Pythagoreans and president of

the Archimedeans, and Gordon Welchman was

a student at Sydney Sussex College and honor-

ary vice president of the New Pythagoreans.

b Kilburn and Tootill were also students in someof Newman’s classes.

ON E O F T H E preeminent fig-

ures in the early history of

computer design was TomKilburn. Over the course

of some 30 years, he made

significant contributions to the development of five historically signifi-

cant computers. Although a natural

team leader possessed of a somewhat

dominating personality, who inspiredin those who worked closely with him

great loyalty and affection, Kilburn

was, on casual acquaintance, a self-contained man who chose his words

with care.

Tom Kilburn was born August 11,1921, in West Yorkshire, England. His

father, John William Kilburn, was a

statistical clerk who rose to become acompany secretary.13 Tom had a some-

what specialized education at Wheel- wright Grammar School having been

permitted by his headmaster to study

almost nothing else from around theage of 14. It was hardly surprising

therefore he emerged from school assomething of a mathematical special-ist. In 1940, Kilburn went Sidney Sus-

sex College, in Cambridge, with sev-

eral scholarships. Wartime courses atCambridge were somewhat truncated

and in 1942, Kilburn graduated with

First Class Honors in Part I of the

Mathematical Tripos and in the pre-liminary examination for Part II.

During the Second World War,

many Cambridge mathematics dons were absent from the university serv-

ing at Bletchley Park and elsewhere.

In spite of this, there remained a livelymathematical community in which

Kilburn played a full part. As the Sid-

ney Sussex college representative inthe New Pythagoreans (a subgroup of

the Cambridge University Mathemati-

cal Society), Kilburn almost certainly

came into contact with a number ofpeople who later went on to play a part

in the development of computing.

Geoff Tootill and Gordon Welchman were, like Kilburn, officers of the New

DOI:10.1145/2594290 David Anderson

Tom Kilburn.

http://dx.doi.org/10.1145/2594290

http://dx.doi.org/10.1145/2594290



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36 COMMUNICATIONS OF THE ACM | MAY 2014 | VOL. 57 | NO. 5

chester Baby was conceived, funded,

and developed as well as the roles

played by various actors in the proj-

ect is somewhat complicated.4,5 The

dominant historical narrative has

come univocally from the engineering

tradition and has generally paid littleattention to the contribution made

by people like M.H.A. Newman andP.M.S. Blackett.3

What is not in doubt is that the

machine itself was the first workingexample of a digital electronic stored

program computer. However, its sig-

nificance for the historian of comput-

ing is not that it was an iconic first butthat it provided the foundation that

Manchester used to build itself into a

leading center for the emerging com-puter science field.

Mark I and Mercury

Kilburn’s original intention had been

to return to TRE after the Manchester

Baby was completed, but the successof the Baby was such that the Ministry

of Supply quickly awarded a contract to

Ferranti to design and build a full-scalecommercial computer to Williams’

specification. An important initial step

was to construct a prototype machine,d

the Manchester Mark I, which was to

be produced at the university. It was

clear to all that Kilburn was vital to thenew project, and Williams, partly with

the inducement of a lecturing post, wasable to persuade him to remain at the

university to work on the prototype.

By the autumn of 1949, the Man-chester Mark I, now with backup drum

store, was complete, and ran continu-

ously thereafter for almost a year. Be-

tween 1951 and 1957 approximatelynine of the Ferranti production versions

of the Mark I machines were sold.

Over the three years since the Baby

was completed, two important shiftsof responsibility had taken place. First,

Max Newman came to the conclusionhaving provided the initial impetus

and leadership in the development

of the Baby that further computer development required engineers rather

than mathematicians to be in the driv-

ing seat. Newman’s withdrawal left

Williams in sole charge, but Williams,

d Actually, the process involved developing a

series of successively more complex proto-type machines.

ly to have come into contact with Alan

Turing, who spent most of 1937–1938

at Princeton based in the world-lead-

ing research group in mathematicallogic headed by Alonzo Church before

taking up his position at for Bletchley

Park in 1939. It is also unlikely that Kil-burn read “On Computable Numbers”

as an undergraduate because his math-ematical taste was more applied thanpure: “[P]ure mathematics seemed ex-

tremely abstract. I was the sort of per-

son who was always prepared to acceptthat two and two are four, whereas I’d

spent the first term at Cambridge in

one of Newman’s lectures proving that

this was so. Whilst it was all very inter-esting—I mean one could appreciate

the beauty of it—it left me rather cold.

At the end of it, you didn’t seem to be

much further forward…”

6

War Service

At some point during his final year atCambridge, Kilburn attended a talk

given by C.P. Snow,c who was visiting

universities recruiting people for un-specified war work. By his own account,

Kilburn had some fairly settled ideas

about what he wanted to do for the wareffort: “It seems silly but if I could have

joined the RAF as a pilot, I would have

done that, but I was relegated to naviga-

tor or some such, and that was not quiteso appealing. It sounds egotistical but

I like to lead. I like to be in charge and

I didn’t fancy the idea of being drivenand crashed by some other character. I

wanted to do my own driving and crash-

ing. It’s on these sorts of whims that lifeis founded—it’s not through any pro-

found thought is it? You take advantage

of what’s there at the time.”6

Having ruled out service in theRAF, Kilburn enrolled on a number

of short courses in electronics and

magnetism. He was assigned to theTelecommunications Research Es-tablishment (TRE), Malvern, where

he joined Group 19, led by F.C. Wil-

liams. He was not, however, greeted with much enthusiasm. Williams had

requested an extra person to join his

team, and Kilburn was the person they

c Originally trained as a chemist at Leicester

and a physicist at Cambridge, Charles Percy

Snow (Baron Snow of Leicester) was midway

through his four years of service as technical

director of the Ministry of Labor at the time ofthis talk.

sent. The other members of Williams’

group were all around 30 years old

with an average of 10 years practical

experience in electronics. By contrast,Kilburn was 21 years old and, prior to

being drafted, had not the least inter-

est in electronics or electronic equip-ment of any kind. Williams, whose

group was responsible for designingand debugging electronic circuitry andfor solving problems encountered by

other groups, made no attempt to hide

his disappointment at being offeredsomeone so inexperienced.

The Manchester Baby

By the end of the war Kilburn was well

settled domestically, having married

Irene Marsden in 1943, and profes-

sionally he had, despite such an in-

auspicious beginning, become an im-portant member of Williams’ team.

Kilburn had achieved the rank of act-ing scientific officer. In 1946, Williams

left TRE to take up the Edward Stocks

Massey Chair of Electro-Technics atthe Victoria University of Manchester.

It was Williams’ intention to continue

his work on the development of the

cathode ray tube (CRT) memory, andhe arranged for Kilburn to work with

him at Manchester under secondment

from TRE. By the end of 1947, Williams

and Kilburn had developed a CRT thatcould store patterns over long periods.

But as Kilburn put it, “the only way totest whether the cathode ray tube sys-

tem would work in a computer was, in

fact, to build a computer.”8

The story of precisely how the Man-

Kilburn’s plan withthe Muse projectwas to develop areally large fastmachine that wouldmake full useof both existingand emergingtechnology.



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C O U R T E S Y O F U N I V E R S I T Y O F M A N C H E S T E R / W W W . D I G I T A L 6 0 . O R G

who never had much interest in com-

puting as such, fairly quickly passed

effective control of further develop-

ments to Kilburn.In 1951, once again following a pro-

cess of incremental development, Kil-

burn began working toward a Mark IIcomputer that was known as the mega-

cycle machine, or Meg. It replaced theMark I valve diodes with solid-state

versions and offered a tenfold increase

in clock rate together with greatly im-

proved reliability and floating-pointoperation. The serial CRT memory,

which was already running at a near

optimal rate in the Mark I, threatened

to act as a performance bottleneck forthe Meg. Kilburn’s solution was to de-

sign a 10-bit parallel CRT memory.

Meg first operated successfully in

the summer of 1954, and Ferranti developed a commercial version of Meg

under the name Mercury. In all, 19 Mer-cury computers were sold, of which six

were purchased by overseas customers.

Transistor Computers

Kilburn led a Manchester design team

consisting of Dai Edwards and Tommy

Thomas, who concentrated on theMeg, together with Dick Grimsdale,

and Douglas Webb, who were simul-

taneously working on what was origi-

nally a research project looking intodeveloping the smallest possible eco-

nomic computer.e It was soon clear agreat deal of valuable experience could

be gained by using transistors to build

the machine. Two prototype transistorcomputers were commissioned, both

of which made use of a pseudo two-

address instruction format and per-mitted optimum programming. The

48-bit machine produced in November

1953, which is widely acknowledged tohave been the world’s first operational

transistor computer, had 550 diodesand 92 point-contact transistors, was

manufactured by STC. A somewhat en-hanced version of the transistor com-

puter was completed in April 1955, this

time boasting some 1,300 diodes and200 point-contact transistors.10

In 1956, the Metropolitan Vick-

ers Electrical Company adapted the

design of the experimental transistorcomputer to allow the use of junction

e E.M. Dunstan also joined in 1954 and workedon drum storage.

transistors and manufactured six tran-

sistor machines, mainly for internal

use, under the name Metrovick 950.From the perspective of Kilburn and

his team, the most important aspect of

the transistor computer was the earlyexperience it gave them in transistor

circuit techniques.11

Muse and AtlasKilburn’s plan with the Muse (micro-

second) project was to develop a reallylarge fast machine that would make

full use of both existing and emerg-

ing technology. He succeeded admira-bly; Muse used “multiprogramming,

job scheduling, spooling, interrupts,

pipelining, interleaved storage, au-tonomous transfer units, virtual stor-

age and paging—though none of these

techniques had been invented when

the project started in 1956.”10

Muse can be considered comparablein scope and ambition to the IBM Stretch

and Univac LARC projects, but Kilburn

was under no illusion that the Depart-

ment of Electrical Engineering had suf-ficient resources available to complete,

without assistance, a project of this scale

and complexity. His initial attempts toelicit Ferranti or the government’s sup-

port for the Muse proposal were unsuc-

cessful, so the decision was taken toproceed instead with a trimmed-down

version of the original scheme. How-

ever, in January 1959, Ferranti, with

Tom Kilburn (left) and F.C. Williams with the Manchester Baby.

£300,000 in backing from the National

Research Development Corporation

(NRDC), decided to participate in theproject, now renamed Atlas.11

Among the innovations introduced

in the Atlas was a scheme that let pro-grammers treat drum stores as if they

were core storage. An innovative pro-

gram called the supervisor managed

drum transfers. The one-level-store con-cept —the idea of a fast and a slow store

appearing as a single fast store—was animportant precursor to virtual memory.

Kilburn was not only responsible

for the management of the project but

also played a part in the circuit design,including work on an adder with a fast

carry path.13 In general, however, he re-

lied substantially on the experienced

teams he had established over a num-

ber of years. Three Atlas systems wereeventually built and installed at the

universities of Manchester and Lon-don and at the Rutherford Laboratory.In 1960, Kilburn was appointed a pro-

fessor of computer engineering in the

Department of Electrical Engineering.

Department of Computer Science

In addition to his considerable con-tribution to early computer design,

Kilburn also did much to establish

computing as an academic disciplinein the U.K. higher education curricu-

lum. Starting in 1963, he spent several

years establishing and organizing a



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38 COMMUNICATIONS OF THE ACM | MAY 2014 | VOL. 57 | NO. 5

to benefit the company persuaded the

Science Research Council (SRC) to as-

sist the project by awarding the uni-

versity a £630,000 grant over a five-yearperiod.

It was a fruitful collaboration. How-

ever, an initial failure by InternationalComputers Limited (ICL) (which by

then had merged with ICT) to acknowl-edge the extent to which the MU5 hadinfluenced their 2900 series concerned

the SRC, outraged Kilburn, and led to a

long-running dispute that was not fullysettled until after Kilburn’s retirement

in 1981.

Retirement

In order to spend more time with his

wife, Kilburn retired early at age 60. Un-

fortunately, Irene Kilburn died just two

weeks before his planned retirement.

1

After that, he continued to spend one day

each month in his old department, but

the majority of his time was spent withhis son and daughter, gardening, play-

ing the piano, and following the Man-

chester United Football Club. He died inManchester, U.K., in January 2001.

References

1. Anderson, D.P. An interview with Maurice Wilkes.Commun. ACM 52, 9 (Feb. 2009), 39–42.

2. Anderson, D.P. Max Newman: Forgotten man of earlyBritish computing. Commun. ACM 56 , 5 (May 2013),29–31.

3. Anderson, D.P. Patrick Blackett: Providing ‘white heat’to the British computing revolution. Commun. ACM 56 ,12 (Dec. 2013), 26–28.

4. Anderson, D.P. The contribution of M.H.A. Newmanand his mathematicians to the creation of theManchester ‘Baby’. The British Society for the Historyof Mathematics Bulletin 24, 1 (2009), 27–39.

5. Anderson, D.P. Was the Manchester Baby conceivedat Bletchley Park? In Proceedings of the ElectronicWorkshops Computing, British Computer Society ,2007; http://www.bcs.org/upload/pdf/ewic_tur04_paper3.pdf.

6. Bowker, G. and Giordano, R. Interview with TomKilburn. IEEE Annals of the History of Computing 15 , 5(1993), 17–32.

7. Ibbett, R.N. The University of Manchester MU5project. IEEE Annals of the History of Computing 21, 1(Jan. 1999), 24–33.

8. Kilburn, T. From cathode ray tube to Ferranti MarkI resurrection. Resurrection: The Bulletin of the

Computer Conservation Society 1, 2 (Feb. 1990), 16–20.9. Kilburn, T. et al. A system design proposal. IFIP

Congress 2 (1968), 806–811.10. Lavington, S.H. A History of Manchester Computers,

2nd ed., British Computer Society, 1998.11. Lavington, S.H. The Manchester Mark I and Atlas:

A historical perspective. Commun. ACM 21, 1 (Jan.1978), 4–12.

12. Morris, D. Early computers at Manchester University.Computer Resurrection 1, 4 (1992).

13. Wilkes, M. and Kahn, H.J. Tom Kilburn CBE FREng. 11August 1921–17 January 2001. Biographical Memoirsof the Fellows of the Royal Society. The Royal Societyof London (2003), 283–297.

David Anderson ([email protected]) is the CiTECHResearch Centre Director at the School of CreativeTechnologies, University of Portsmouth, U.K.

Copyright held by Author.

new Department of Computer Science,

the first of its kind in the U.K. The in-

tention was to provide a natural home

for computer research, a sound basefor future projects, and undergraduate

courses in computer science. Kilburn,

now translated into a professor of com-puter science, was the inaugural head of

department, and had 12 academic staffunder him. Directly reflecting Kilburn’spersonal strengths and his professional

experience, Manchester placed more

emphasis on hardware than many ofthe other computer science depart-

ments that followed it, most of which

sprang from a mathematical lineage

rather from engineering. Kilburn wenton to serve as the dean of the Faculty of

Science from 1970 to 1972 and pro vice

chancellor between 1976 and 1979.

MU5

In 1966, Kilburn embarked on what was to be his last major computing

project: the MU5. The Atlas had been

operational for four years, and theMU5’s main focus was to provide a

computer architecture geared toward

the efficient running of programs writ-

ten in high-level languages. The MU5 was conceived as a range of three ma-

chines—a small inexpensive computer,

a high-spec scientific computer with 20

times the throughput of the Atlas, anda multiprocessor—but only the second

was actually developed.12 The MU5’soriginal design proposal was set out in

1968 at the Edinburgh International

Federation for Information Processing(IFIP) conference in a paper authored

jointly by Kilburn, Derrick Morris, Jeff

Rohl, and Frank Sumner.7,9

An interesting technical aspect of the

MU5 was the associative name store in

which frequently used scalar variables would automatically reside in a fast

cache store. Morris explained, “This wasas a result of an analysis of the Atlas soft-

ware, especially the instruction code.

We learnt something about the frequen-

cy of use of operands and control struc-tures. The order code accommodated

string functions and vector functions.”12

The university secured the coopera-

tion of International Computers and

Tabulators (ICT), which made con-struction facilities available at cost

and provided five staff to work on the

project. The university’s relationship

with ICT and the potential it created



C o p y r i g h t o f C o m m u n i c a t i o n s o f t h e A C M i s t h e p r o p e r t y o f A s s o c i a t i o n f o r C o m p u t i n g

M a c h i n e r y a n d i t s c o n t e n t m a y n o t b e c o p i e d o r e m a i l e d t o m u l t i p l e s i t e s o r p o s t e d t o a

l i s t s e r v w i t h o u t t h e c o p y r i g h t h o l d e r ' s e x p r e s s w r i t t e n p e r m i s s i o n . H o w e v e r , u s e r s m a y p r i n t ,

d o w n l o a d , o r e m a i l a r t i c l e s f o r i n d i v i d u a l u s e .

a tale of five computers

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